 A very good evening aspirants, I have an announcement for you, see checking your progress and assessing it is as important as studying regularly for the UPSA civil services examination. And well, again Shankaray's academy is going to lend you a hand in this, yes Shankaray's academy is going to help you in assessing your problems preparation for 2022 preliminary examination. And for this Shankaray's academy is conducting all India problems mock test, it is a free mock test, it will be conducted in offline as well as online mode across 13 centres. And note down the dates here, it will be conducted on 15, 22nd and 29th of May. So I request the viewers to register for the free all India problems mock test for assessing your preparation. So with this announcement let us get to the Hindi news analysis for the newspaper edition dated 25th of April 2022. These are the articles I have taken for discussion today. Many of these topics are important in problems perspective, so pay attention and at the end I also have a quiz question for you. So without wasting much time, let us get to the discussion. So we are going to start our discussion with this news article, it talks about the effective steps that were taken to arrest the rampant growth of an invasive vegetation in the forest areas of Neil Geary's biosphere reserve. And here we are talking about the invasive species called Senna spectabilis. According to the article, this species has created a serious concern for the conservation of wildlife habitats of the western guards. And the recent study has revealed that this invasive species has now spread through the most iconic wildlife habitats of the western guards. And this is destroying the habitats of animals by pushing out native flora. So in this discussion we are going to see what is this Senna spectabilis and why it is called as an invasive species. But first let us understand what do we mean by invasive species? See it is a species that is non-native to the ecosystem which is under consideration. This is the first feature that is that species is alien to that ecosystem. Now the second feature is the introduction of such species causes or is likely to cause economic harm or environmental harm or even harm to human health. So these two features or characteristics makes a species as invasive. Now how these species are introduced? It could be released accidentally or even by people. Actually human actions are the primary means of invasive species introductions. So now let us come to the Senna spectabilis. Now this is an invasive plant species. So this is how it looks and this is the flower and the leaves. Now this species belongs to the Fabercius family and it is grown as an ornamental plant across tropical America. Ornamental plant means it is grown for its attractive appearance. But note that this species is considered to be native to South America and it was introduced to Central America in the West Indies. Now let us see some features of this species. See it can grow 7 to 18 meters tall and it produces yellow flowers as we just saw in the picture. And it is also commonly used in traditional medicine for many years. Even pharmacological studies reveal that this species possesses significant properties such as antibacterial property, anti-boyfilm property, anti-fungal properties and antioxidant properties. But even though it has these medicinal properties and uses, still this species is considered an environmental weed. Why? Because it grows extremely fast. See it flowers and sets seed profusely and the trees start to flower in two years itself. Plus the survival rate of the seeds are 95 to 19 percentage and even these seeds can survive in soil for 8 to 9 years. Plus if you even debark this tree then also it suddenly starts flowering just for survival. So it even re-sprouts immediately when cut. So from this itself you can understand that how hard it is to get rid of this tree. So this is the first cause of concern. Now second concern is because of its allelopathic traits. See allelopathic traits refers to some chemical traits which it has and through which it affects the other plants. See the allelopathic traits of this species prevent other plants from growing under it. So how this happened? See it creates a chemical warfare where the shed leaves of this species decompose and it changes the chemical composition of the soil itself. So this makes it unsuitable for the growth of other plant species. And this is how it pushes out the native plant species and through this the native grasses and herbs get completely wiped out. So this in way affects the herbivores also because they are deprived of their food and according to studies it was found that herbivores do not consume the leaves of Senna Spectapolis. So this actually decreases the carrying capacity of forests. That is the capacity to feed wildlife is drastically declining under the invasion of this species. Because of all these issues only already in places like Australia, Uganda and Cuba Senna Spectapolis is considered as invisible. And now we have found that it has made its way to Indian forests especially to the South Indian forests and it is affecting the western guards. See it is found in Mutanga and Tulpeyti ecological centers where around 10 percentage of area is affected by Senna Spectapolis. This is around 2 percentage of the total area of Wynard Wildlife Sanctuary. And according to the recent research it is found that the species is spreading to the rest of Wynard Wildlife Sanctuary and it is even spreading to nearby reserves like Bandipur reserve, Nagarhole and Mudumalai reserves. And we know that these places are biological hot spots and if this species survives there then it means other herbivores will be pushed out of its habitat. But how did the species get into India? Especially in the Wynard region. See it all started in the year 1970 when Senna seeds from abroad were distributed to people across Wynard as a social forestry initiative. Why it was distributed? Because we saw that it has beautiful flowers right? And this is the reason it was distributed to people. So if you find this species around your home or in your place or in your environment please take measures to remove it. So what are some of the measures taken to eradicate the species? It includes gridling of trees and uprooting of the young plants. Gridling means it is cut through the bark all the way around. So this actually kills the tree. There is another initiative taken by the Kerala Environment Department. It is to plant bamboo saplings in between the Senna with the hope that bamboo will overcome the Senna. So these two measures can be taken. So these are the few facts that you have to know about Senna Spectabulous and its invasive nature. Now before concluding let me tell you other important most serious invasive species in India. It includes Altanantara, Phylloxeroidus, then Cassia uniflora, Chromoliana odorata, Acornia, Craspice, then Lantanacamara, Parthenium, Hysterophores, Presophus, Julephora. All these are invasive plant species. Now you would have heard about Presophus, Julephora. Actually we already have a problem's question on this species. So you can understand how important this topic is for the problems and the facts which you just saw in the discussion is important for mains also because invasive species affect the biodiversity. So with these facts in mind let us get to the next discussion. So let us take up this news article for discussion now. It talks about the Mridangamastro, TK Murthy. See he was presented with the Subhash Chandra Memorial Award for excellence in percussion. Here T.H. Subhash Chandra on whose remembrance the award is named used to play and teach several instruments including Ghatam, Mridangam, Kanjira etc. But today we are only going to focus on Mridangam and Konakol which is related to it. So as you can understand Mridangam is a musical instrument and its origin can be traced back to ancient Indian mythology. Now here the term Mridangam or Mridangam comes from the Sanskrit words Mrid and Ang which literally means clay body. But over the years Mridangam was made by different types of wood and the sound changed over time. So know that today Mridangam is made from a large piece of hollowed out jackfruit wood. Now this hollow large piece is covered on the two sides that is there are two mouths or two openings. It is covered with goat skin and they are attached to each other with tightly bound leather straps. But note that the two sides of the drum are different sizes. This is because it enables you to get bass and treble sounds from one drum. So where this musical instrument is used see this instrument is used in South Indian music or in the karnatic form of music and it is the main percussion instrument there. So when you say percussion instrument it means that this instrument is played by striking with hand or with a strike or with a beater or by shaking. And in case of Mridangam they play it by striking with hand. So this musical instrument is used to accompany vocalists and all types of melodic instruments of South India. It is also used as an accompaniment for Bharat Natya which is a classical dance of Tamil Nadu and even other forms of Indian dances. Now then what about Konakol. So this term is closely related to Mridangam. What is it? Konakol is the art of recitation of solkattar. What is solkattar? It is the vocal syllable of the Mridangam. So we can say that solkattar is the drumming language and this language recitation is called as konakol. Now here the term konakol comes from the words koni which means to recite in Telugu. So this Telugu word was adopted in Tamil and it was joined with kol. Kol means rule. So that means this recitation rules the art of Mridangam. That is it leads the Mridangam. Also know that konakol is used as a reference for all karnatic music and since Mridangam is the most versatile of the karnatic percussion instrument konakol is closely allied with the sounds of Mridangam. It is an integral part of the training of the Mridangist. It is also used extensively in dance music of Bharat Natya and Kuchupudi. So in these dances it is intermixed in these songs and it often leads the Mridangam. So just remember that konakol is related to Mridangam especially to karnatic music also and Mridangam is a percussion instrument. So these are the few facts that you have to know about Mridangam. Now let us move on to the next discussion. So this discussion is going to be based on this oped article. See this article talks about the serious viral infection polio. Now why we are discussing about polio? Because there are news of wild polio virus type 1 infection in Malawi and there is also a reported polio outbreak in Israel. On this backdrop only this oped article has been written. And according to the article the outbreak in Israel is caused by a virus called as circulating vaccine derived polio virus type 3. So that is why in this discussion let us have a basic understanding of the polio virus. Then we will see its types. Mainly we will cover the concerning factors related to polio. And finally we will also see the steps taken to eradicate polio. Now before that see here this is the syllabus relevant to this discussion. First let us understand about polio. See polio is also called as poliomyelitis. It is a highly infectious disease. It is a disabling and life-threatening disease caused by the polio virus. This polio virus belongs to the family Picorinaviridae. Now this is how the polio virus looks like. And as I said it is highly infectious. So how this virus is transmitted? It is transmitted from one person to another person. And this is mainly through the fecal oral route by a common vehicle. And here the common vehicle could be contaminated water or contaminated food. See what this virus does is once it is transmitted to one person it multiplies in their intestine. And from there it invades the nervous system of that person and causes paralysis. So here you should remember that when it comes to polio virus humans are the only known disavoir of this virus. So it is transmitted most frequently by a person having the infection. And as we already know it largely affects children. Now generally there are two basic patterns of polio infection. The first pattern is minor illness. This does not involve the central nervous system. So this is sometimes called as the abortive poliomyelitis. Now the second one is a major illness because this involves the central nervous system. Therefore the second pattern could be paralytic or non-paralytic also. Paralytic means it causes paralysis. Now let us come to the types of polio virus. See there are three individual and immunologically distinct wild polio virus strains. They are wild polio virus type 1, wild polio virus type 2 and wild polio virus type 3. In short we call them as WPV1, WPV2, WPV3. Now remember that the symptoms of all these three strains are identical. That is they all can cause irreversible paralysis or even death. But still they are distinct. Why? Because there are genetic and immunologic differences which makes these three strains as three separate viruses. And that is why each strain must be eradicated individually. So now comes the question of can polio be cured? Actually there is no cure for polio. It can only be prevented by immunization. That is vaccination. In childhood we all got the polio vaccine. It is given multiple times so that a child's life is protected. So now let's come to the vaccination. Actually there are two different kinds of vaccination available for polio. The first one is an inactivated polio vaccine. In short IPV. Remember this inactivated polio vaccine? Here inactivated means killed. So this IPV is produced from wild type polio virus strains of each serotype that have been inactivated or killed with formalin. Now this is an injectable vaccine. So it can be administered alone or in combination with other vaccines also. Now what this IPV does is it produces antibodies in the blood to all the three types of polio viruses. Now when there is infection these antibodies prevent the spread of the virus to the central nervous system and thereby they protect against paralysis. So in this way IPV prevents infection. But note that it does not stop transmission of the virus. Now let us come to the next kind. It is the live attenuated oral polio vaccine. In short OPV. Here attenuated means weakened. So this OPV consists of a mixture of live attenuated polio virus strains of each of the three serotypes. So here what happens is for several weeks after vaccination the vaccine virus replicates in the intestine and then it is excreted in the feces also. And thereby it can be spread to the people who are in close contact with this feces. This means that in areas where there is poor hygiene and sanitation vaccination with OPV can actually result in passive immunization of people who have not been directly vaccinated. And that is why OPV is a preferred option when there is a polio outbreak. Why because as I just said even those who are not vaccinated are passively immunized when they come in contact with the vaccinated person. So here three doses of OPV are given and after this a person becomes immune for life and they can no longer transmit the virus to others if even they are exposed again. But note that there are three different types of this OPV vaccine. One is the trivalent OPV. It protects against polio virus type 1, 2 and 3. That is trivalent all the three. Next one is bivalent OPV. It protects against type 1 and 3. And the third one is monovalent. This one protects against either type 1 or type 3. But not both okay. So overall note that both the vaccines are highly effective against all three types of polio viruses. So these are the basics that you need to know about polio and the immunization process. Now let us come to the article discussion. Here it talks about the measures taken to eradicate polio. See in the year 1988 the World Health Assembly adopted a resolution for the worldwide eradication of polio. Now this resolution marks the launch of global polio eradication initiative. Along with this the Rotary International also launched its polio plus project in 1985. Under this polio plus project polio vaccines were provided to the children under the age of five of all developing countries. And this was done before 2005. So because of these measures out of the six WHO regions three of them actually achieved the goal of eradicating polio in their territories by 2000s or before 2000. Which are the three regions they are America, Europe and Western Pacific. So that means in the remaining regions it was not eradicated. So that is why after that WHO's task was confided to the southern arc of the remaining regions. And these regions include Africa, Eastern Mediterranean and Southeast Asia. So in these regions WHO failed to eradicate polio by 2000. And because of this after that WHO revised its target every 45 years. And now the target is set at 2026. So even now it is not eradicated remember this. See even though it is not eradicated the numbers have been significantly reduced. That we have to accept. See as per these statistics the cases have tremendously decreased by over 99% since the year 1988. See at that time there was an estimated 350,000 cases in more than 125 polio pandemic countries. But in 2019 there were only 175 reported cases overall. So you can see how much it has reduced. And thanks to the immunization process. Now along with this the statistics also provide us another data which is out of the three strains of wild polio virus. There is type 1, type 2 and type 3. The type 2 was eradicated in 1999 itself. And regarding type 3 no cases have been found since the last reported case in Nigeria in 2012. So because of this both the strains there is type 2 and type 3 have been officially certified as globally eradicated. So then what about type 1? See as of 2020 wild polio virus type 1 is still prevalent. It affected two countries. One is Pakistan and the other one is Afghanistan. But now I said in the beginning that there are certain problems associated with polio. What are these? See the reduction of polio cases happened because of vaccination. We just know so. But what if vaccination itself becomes a problem? You may think now how vaccine can turn into a problem? It is only used to eradicate the problem right? See actually it becomes a problem in some cases. For example the OPV that is oral polio vaccine itself may cause VAPP. What is VAPP? Vaccine associated paralytic polio. This VAPP can be caused in vaccinated children and even in unvaccinated child contacts. Here when the vaccinated children get VAPP it is called as vaccinated VAPP. And when the unvaccinated people get VAPP it is called as contact VAPP. So now let us see what is this VAPP? Now when we saw about OPV I said that it consists of a mixture of live attenuated polio virus strains. It is live but it is weakened. The problem is even this virus is weakened it is still alive in the oral vaccine. So in rare cases it may invade the nervous system and cause paralysis. And this is what is called as the VAPP. Vaccine associated paralytic polio. And according to WHO this is mainly triggered by immune deficiency in the person. So first this VAPP happens in the children who got vaccinated. So this is the main concern with polio. But there is also another concern which is the contact VAPP. That is this will happen when the unvaccinated children also come in contact with the vaccinated children and if the vaccinated children have developed VAPP and when these unvaccinated children come in contact with them they will also get affected by the virus. And this scenario is what is called as the contact VAPP. And according to WHO the commonest cause of a vaccinated VAPP is type 3 vaccine virus. Whereas the cause for contact VAPP is type 2 vaccine virus. So are these the only two concerns with polio? No that is also a third concern. It is about the circulating vaccine derived polio virus type 3. Ensured CVD PV3. Actually this is also a VAPP. See the difference here is that in the circulating polio virus type 3, the virus in OPV deatenuates by mutation. Deatenuates means it becomes stronger. So it acquires transmission efficiency and neuro virulence. What is neuro virulence? It means it develops the tendency to affect the central nervous system. So these are the three concerns associated with polio. Now you may ask where these side effects not known before. Actually it was known already since 1964. And that is why for avoiding VAPP, rich countries immunize children with the inactivated polio virus vaccine that is with IPV. Because IPV is completely safe. Why? IPV contains the inactivated or killed virus. And this is the reason it is considered safe compared to the OPV. So you can understand that all the three concerns are associated with OPV only. Then why to use OPV? We can directly go for IPV right. Why to have an OPV vaccine? This is because of certain benefits that are associated with OPVs. See there is a benefit risk balance in OPV. What is the benefit risk balance? See when the risk of wild polio virus polio was annually 2 per 1000 school children, the risk of VAPP was much lesser. It was only 1 per 150,000 births. So here the benefit is more than the risk. But remember when the risk of death or paralysis falls low, the benefit risk ratio reverses. That is here the risk becomes more. So because of this benefit risk balance, OPV was still used. But some corrections were also made. For example after the WPV2 was eradicated in 1999, the benefit of type 2 vaccine virus became useless. So here came the ethical problem of risk without the benefit. This problem was actually neglected until circulating vaccine derived polio virus type 2 caused several outbreaks. So because of this it forced the countries to switch from trivalent vaccine to bivalent vaccine in 2016. We saw that in trivalent it protects against all the three types. One, two and three. So it has attenuated virus of all the three types. But in bivalent only one and three are present. Now since after WPV2 was eradicated, we need not need type 2 vaccine virus right? And that is why they shifted to bivalent. Then what about type 3? It was also globally eradicated in 2012, but it was not done. That is the vaccine virus type 3 had to be removed for avoiding VAPP. But it was not done. Here we should remember that according to the author, no agency has any right to cause VAPP in the name of eradication, especially after this type 3 has been eradicated. And now because of this only in Israel we have CVD-PV3, that is circulating vaccine derived polio virus type 3. And it has caused the outbreak. As of now, seven children have already been paralyzed and all of them were unvaccinated. But we saw that vaccinated children get the CVD type of virus right? Then how these children got? It is because of the contact VAPP. Remember that. So that means if seven children are already paralyzed who are unvaccinated, many children have already been affected. According to the data, the risk of paralysis with WPV3 is 1 in 1000 infected children. So if seven children have been paralyzed, then that means already 7000 unvaccinated children were infected. If this is the case with Israel, then what will happen with India? Because our population is much more than Israel. Israel's population is less than 10 million. But ours is 1400 million. See even though the probability of CVD-PV3 outbreak is low in India, but because of our population size, still the impact will be enormous. And that is why author has concluded with a suggestion for India. Author has suggested that India must withdraw type 3 vaccine, that is the monovalent type 3. We saw that OPV vaccine has three types and among them we had monovalent also. In that we had monovalent type 1 and monovalent type 3. Now author is suggesting that India must withdraw this monovalent type 3 and we should continue with monovalent type 1 OPV. But this should only continue until IPV reaches 85 to 90 percentage coverage. So that we do not get a new outbreak called as CVD-PV1. So slowly we must withdraw monovalent type 3 vaccine. So these are the few points that you have to note about polio. In this discussion we saw what is polio. It is a highly infectious disease. It causes paralysis. It is caused by a virus called polio virus from the picornoviridae family. And this is transmitted from person to person through fecal oral route. This virus replicates in the intestine and invades the nervous system causing paralysis. And humans are the only known reservoir of this polio virus. It largely affects children. It has two patterns of illness. One is the minor illness where CNS is not affected. And in the major illness central nervous system is affected. And it may cause paralysis. And there are three types of polio virus. One is wild polio virus type 1, type 2 and type 3. All these three are identical. But there are genetic and neurologic differences. So they have to be eradicated individually. And finally we saw that there is no cure for polio. And it is only prevented through immunization. So from that we saw about the vaccination. One is the IPV inactivated polio vaccine where the virus strain is killed and used. And the next type is OPV which is oral polio vaccine. Here it is a live attenuated vaccine. So here the virus strain is weakened and not killed. But this OPV can result in passive immunization of people. And there are three different types of OPV. Trivalent OPV, bivalent OPV and monovalent OPVs. Trivalent is for 1, 2 and 3. Bivalent is for both 1 and 3. And monovalent could be either for type 1 or type 3. Then we saw that WHO had taken many measures. There was a resolution for the launch of Global Polio Eradication Initiative. Then Rotary International launched Polio Plus project. And because of these initiatives in America, Europe and Western Pacific, Polio was eradicated before 2000. But in Africa, Eastern Mediterranean and Southeast it was not eradicated. And as of now the target of eradicating is set by 2026. But the prevalence of outbreak has been reduced to a larger extent. And we saw that globally type 2 and type 3 have been declared globally eradicated. But type 1 is still affecting countries like Pakistan and Afghanistan. Then we saw the problems with polio, especially the OPV. It causes VAPP. There are two types. One is vaccinated VPP and second one is contact VPP. And there is also third concern which is circulating vaccine derived polio virus type. This one de-attend weights the virus by mutations and causes neuro virulence. Then we saw that OPV was still continued because of the benefit-risk balance that it had. And finally we saw the conclusion that India must withdraw type 3 vaccine. And it should continue with monovalent type 1 until the IPV coverage reaches 85 to 90 percentage. So these are the few points that you have to remember from this discussion on polio. Now let us go to the next discussion. So this news article talks about the 150th birth anniversary celebrations of Sri Aurobindo. See the celebrations have been launched by our home minister at Puducherry University yesterday. So let us see few relevant facts about Sri Aurobindo and his contributions. Because for these problems this is an important area. See basically Sri Aurobindo stood as an invaluable heritage for our country because he contributed as a poet, nationalist and philosopher. He was born on August 15th of 1872. He was born in Calcutta. So you can understand that this year is the 75th Indian Independence Day. And this day even marks the 150th birth anniversary of Sri Aurobindo. And this is the reason the celebrations have been started now itself. Also know that his original name was Aurobindo Ghost. He was a yogi, seer, philosopher, poet and Indian nationalist as I already said. He also propounded a philosophy of divine life on earth through spiritual evolution. Now let us see a brief history about his life. See he began his education in a Christian convent in Darjeeling and later he was sent to England for further schooling. There he graduated from University of Cambridge and there he also became proficient in two classical European languages of Greek and Latin. Along with that he also became proficient in several modern European languages also. Then he returned to India in 1892 or 1893 period. After that he held various administrative posts and he was also a professor in Baroda which is now called as Vadodara. He also worked in Calcutta. Then later he started focusing on his native culture. Then he began the serious study of yoga. This is why we call him a yogi. And as a part of this he also studied Indian languages including classical Sanskrit. Now most importantly know that he was also a part of Indian freedom struggle from 1902 to 1910. And at that time he also started a newspaper which was called as Bande Mataram. And through this newspaper it is said that he became the first political leader in India to openly put forward the idea of complete independence for the country. But in this period due to his political activities he was also imprisoned in 1908 and then two years later he fled British India. After that he found refuge in the French colony of Pondicherry. This is now called as Pudicherry. It is in south-eastern India bordering Tamil Nadu. So from Pudicherry he devoted the rest of his life to the development of integral yoga. See integral yoga was a new method of spiritual practice evolved by Shri Arbindo. Now the main aim of integral yoga is a spiritual realization that not only liberates man's consciousness but also transforms man's nature. So this included attaining the aim of a fulfilled and spiritually transformed life on earth. Now as a part of this only in Pudicherry that is then Pondicherry he founded a community of spiritual seekers. This community later became the Shri Arbindo ashram in 1926. It was started along with his spiritual collaborator Meera Alfaza. Meera Alfaza is also called as the mother in the ashram. Shri Arbindo interested the work of guiding the seekers to this spiritual collaborator. So in this way the ashram started attracting seekers from many countries throughout the world. Even now we can find that people from many regions go to Pudicherry just to visit this Arbindo ashram. So in this way let us have a brief look at his philosophy of life. See the evolutionary philosophy fundamental to Arbindo's integral yoga is explored in his main prose work which is called as the life divine. It was written in 1939. So here we can find that Arbindo rejected the traditional Indian approach of striving for moksha. What is moksha? It means the liberation from samsara. Samsara is nothing but the cycle of death and rebirth. So that means Arbindo rejected using moksha as a means of reaching happier transcendental planes of existence. What is transcendental? It is nothing but supernatural. He rejected using moksha for this because he held that the terrestrial life itself is the higher evolutionary stage of existence and according to him it is the real goal of creation. So he believed that the basic principles of matter, life and mind would be succeeded through terrestrial evolution only. And according to him this has to be achieved by the principle of super mind as an intermediate power between the two spears of infinite power and the finite power. So overall he aimed to develop a future consciousness that would help to create a joyful life in keeping with the highest goal of creation. He also aimed that this will help to express values such as love, harmony, unity and knowledge and it will also lead us to you know in a path that will successfully make us overcome the age old resistance of dark forces against the efforts to manifest the divine on earth. So as a part of his spiritual journey he authored many literary works. These literary works include philosophical speculations, many treaties on yoga and integral yoga, poetry, plays and even other writings. So let us see some of the important literary works. We already saw the life divine then there is also a work on essays on the yoga then there is collected poems and plays then the synthesis of yoga the human cycle the ideal of human unity then savitri a legend and a symbol and there is also a work called on the veda. So these are the important literary works of Sri Harbindo. Go through this list and remember these names it will be helpful for you in the examination. And finally know that he left this world on December 5th 1950 in Pondicherry. So this was a brief history of Sri Harbindo. We saw what were his contributions to India. We saw his literary work especially his spiritual works etc. With these facts in mind let us get to the next discussion. So let us take up this news article it talks about the zero shadow day. See this day was observed in the Chennai city yesterday that is on Sunday. So in this context let us know what is this zero shadow day and when does it occur. So actually this zero shadow day is a biannual phenomenon. So what does it mean? It is the lack of shadow in the day. This phenomenon is also beautiful and it happens twice a year that is why he said it is a biannual phenomenon and it occurs in places between 23.5 degrees north and 23.5 degrees south latitudes. Now when does it occur and how does it occur? See it occurs when the sun is directly overhead. So at this time its rays are exactly perpendicular to the surface and this will make your shadow exactly under you. So it makes it look like you know there is no shadow. But does it occur often? She has already said it is a biannual phenomenon. That means sun is almost never exactly overhead known but only twice a year. See actually our equator is defined as being perpendicular to its rotational axis. But actually this equator is inclined at 23.5 degrees with respect to the earth's orbit around the sun. Therefore our rotation axis is also tilted at this angle from the axis of revolution around the sun. Now due to the tilt of the axis the daily path of the sun slowly moves northwards and southwards over the period of a year. Now since the tilt angle is 23.5 degrees the southernmost path of the sun is 23.5 degrees south of the equator at the winter solistice which is around 22nd December every year. This means that on this day the sun will be directly overhead at known for places that are on the tropic of Capricorn at 23.5 degrees south latitude. And similarly the path of the sun on summer solistice is 23.5 degrees north of the equator and this is on 21st of June every year. That means on this day the sun is directly overhead at known for the places on the tropic of cancer that is 23.5 degrees north latitude. And we know that the journey of the sun from winter solistice to summer solistice is called Uttarayan and the return journey is called Dakshinayan. So that is why in other places that is the places other than the tropic of Capricorn and the tropic of cancer the no shadow day differs. But ultimately when the location of the sun is highest in the sky or in the zenith position there will be no shadow. So now if we talk about India can it be observed in all places in India? Actually no. As we saw in the beginning it is understood that only in the regions between tropic of cancer and tropic of Capricorn the zero shadow day can be observed. So that means Indian cities like Chennai, Mumbai and Pune they fall between the tropic of cancer and tropic of Capricorn. So they are likely to observe zero shadow day. On the other hand the states which are about tropic of cancer here the phenomenon cannot be observed. We know that the North Indian states are about tropic of cancer and this is the reason even our capital New Delhi cannot observe this day because it does not fall between tropic of cancer and tropic of Capricorn. So these are the few facts that you have to know about zero shadow day. Know that it occurs on 22nd of December that is in winter solstice at the tropic of Capricorn and it occurs in the 21st of June that is in summer solstice at the tropic of cancer. On the other regions that is between these two regions it occurs but the date varies. So with these points in mind let us move on to the next session which is the practice questions discussion session. Let us take up the first practice question which among the following is or are percussion instruments. Drum, piano, mridangam. See as I said in the discussion percussion instruments refer to any instrument that makes a sound when it is hit shaken or beaten. So it is not easy to be a percussionist because it takes a lot of practice to hit an instrument with the right amount of strength in the right place and at the right time. So from our discussion you can easily say that mridangam is played by hitting it. Same with the drum also. Now you may have a doubt about piano. See the vibrations in a piano are initiated by hammers hitting the strings rather than by plucking or by moving a bow across them like in the case of a violin. And because of this reason piano also falls in the realm of percussion instruments. Actually it is also considered as a stringed instrument along with a percussion instrument. So piano is also a percussion instrument and that is why the correct answer to this question is option D all the above. Now let us take up this next question. It is based on Sena Spectabilis. First statement is it is an indigenous plant species of India. This statement is incorrect because indigenous means it is native to India. No it is not. Sena Spectabilis is native to South America and it was introduced to Central America in the West Indies. It was also introduced to South Indian forests. So statement one is incorrect. Now the second statement it increases the primary productivity by serving us food for the herbivores. See this statement is also incorrect. Why because we saw that Sena Spectabilis is an invasive species. So that means it does not increase productivity. If you know this fact you can easily arrive at the correct answer. This species actually affects primary productivity at the ground level. Why because it wipes out grasses and herbs and therefore the herbivores are deprived of their food. And here the question asks for these correct statements. But both the statements are incorrect here. So the correct answer to this question is option D neither one nor two. Now let us take up the third question. It is about Sri Aravindu discussion. First statement he started the newspaper now J1. This statement is incorrect because he did started newspaper and he has also done many literary works. But his newspaper's name was Vande Mataram. And his literary works include essays on the Gita, the synthesis of yoga, the human cycle, the ideal of human unity etc. We saw all this during discussion. But whose publication was Navjivan? It was Gandhiji's. So during his lifetime Gandhiji ran four publications. One of them was Navjivan. Others were Indian Opinion, Young India and Harijan. So first statement is incorrect. Let us take the second statement. He believes in terrestrial evolution and rejects the traditional approach of striving for moksha. This is correct because this is the Aravindu's philosophy of life. He believes in terrestrial evolution and rejects the traditional approach of striving for moksha. So here the question asks for the correct statements. Therefore the correct answer is option B2 only. So with these three questions let us take up the quiz question for the day. It is based on the zero shadow day discussion. Read the question carefully. You can write the answer in the comment section and I'll tell you whether your answer is right or not. So with this quiz question let us take up the main question for the day. This is the main question. Read the question. You can answer the question very easily if you have listened to our today's discussion on polio. You can write the answer and post it in the comment section. So with this we have come to the end of Hindi news analysis for 25th of April. If you like today's session click the like button and subscribe to our channel if you have not subscribed yet. I'll meet you all in my next session. Thank you.